1. Field of the Invention
This invention relates to an operation and maintenance system of a telephone network, and routing of information in the system, in particular.
2. Description of Related Art
In a telephone network, the most important task of the maintenance service of an exchange is to make sure that the exchange will function in failure situations, i.e. to ensure the call switching capability when one unit of the exchange fails. In a failure situation, a faulty unit is disconnected and replaced with a stand-by unit. Maintenance service also includes reporting of charging information, as well as compiling reports on traffic control, alarm and monitoring. The maintenance programs are concentrated in the operation and maintenance unit (OMU) of an operation and maintenance center (OMC) connected to the exchange, in which OMU the necessary files are also located. Operation and maintenance (OM) of various exchanges is thus concentrated in the areal operation and maintenance center (OMC), the task of which is to collect in a centralized manner in the maintenance center of the telephone operator the above-mentioned charging information provided by the operation and maintenance (OM) of the telephone exchanges located within the area, as well as reports on traffic control, alarm, and monitoring. In extensive systems comprising a plurality of areal exchanges, and exchanges connected to them, the management of areal operation and maintenance centers (OMC), and concentrated collecting of their service information in a centralized manner may be subjected to an operation and maintenance center acting as the master controller.
The operation and maintenance centers thus form a so-called OM network (Operation and Maintenance Network), in which each OMC is a network element, which is specialized in collecting and storing the data produced by single exchanges of the system situated below it in the hierarchy. The OMC does not post-process this data, but post-processing is carried out elsewhere, such as in a Network Management Center. Data transmission between different network elements, i.e. OMC's may be implemented via a packet switched data network, which is represented in FIG. 1 by a schematically depicted X.25 network, or via time-slots reserved from semi-permanently connected PCM circuits, or via a network using the common channel signalling system #7 in accordance with the CCITT standard.
FIG. 1 shows an example of an OM-network. At the top of the hierarchy, there is a Network Management Center, NMC, and below it a Main Operation and Maintenance Center functioning as the main controller, and connected to areal Operation and Maintenance Centers OMC. To the last-mentioned, single exchanges and switching centers and exchanges are connected. The main operation and maintenance center is in charge of supervising the entire OM network. It is connected to the network management center NMC e.g. via an OSI interface (Open System Interface) in accordance with the standard.
As appears from FIG. 2, the functions of the operation and maintenance are distributed in an exchange to several microcomputer units, the software located in which is loaded under the control of an operation and maintenance unit OMU. The microcomputer units include identical data management units DMU, which are named according to the dedicated tasks, e.g. charging management unit, performance management unit, traffic monitoring unit, fault control management unit. In addition, they include data communication units DCU, via which analog and digital connections are transferred to the network and from the network. A data communication unit DCU comprises a so-called I/O manager, an interface to an internal message bus of the OMC, and multichannel signalling terminals, as well as serial communication terminals, via which the linkage to the network connecting the exchanges takes place. The microcomputer units comprise mass memories, which may be e.g. hard disks or floppy disks. Messages within the OMC between different units are transferred via a message bus MB. The message bus enables expanding the OMC to fulfil almost any requirements for data traffic and storage capacity, since the expansion may be implemented by adding microcomputer units to the bus according to the need.
When information is directed from one unit to another and from one exchange to another, in other words, when input and output are carried out, routing is performed. Thus, a so-called logical file forms an essential part of the I/O system. A logical file is a certain named gate that may be connected either to a certain number of I/O devices (FIG. 3a), or to other logical files that, in turn, may be connected to an I/O device (FIG. 3b). An alternative, more fitting expression for the term "logical file" would be "logical linkage", as it determines how the routing linkage is carried out. The figures represent a case in which the output data of a program, e.g. a fault control management program, providing the output is directed to an I/O device. The operator may modify the I/O connections of the system by changing the linkages of the logical files. In practice, the I/O devices are displays, terminals, printers, hard disks, disk drives, and magnetic tape units.
Reference is now made to FIGS. 4a and 4b. The program block connected to logical files is termed as an I/O manager. Upon providing an input or an output, i.e. an I/O function via a logical file, a unit, e.g. a fault control management unit, gives its manager a task related to a determined logical file. The I/O manager gives the task to the I/O manager of a second unit, provided that there is a logical file to logical device connection, or to the device driver if it is a question of a connection between a logical file and a device. The control of the I/O functions of the exchange is thus concentrated to the I/O manager of the maintenance and operation computer, which knows and maintains the linkages of the above-mentioned logical files. The I/O managers of different systems communicate with each other via an OM network. The operations may be described as follows: in FIG. 4a, in the section representing input, information is first directed from the I/O device of the operator to the logical file, and from there to an appropriate application program. In FIG. 4b, describing the output function, an application program block first directs the output to a predetermined logical file, and from there it is directed to an I/O device. The application program thus only recognizes the logical file to which it directs the output, or from which it reads the output, and only the I/O manager knows which one is the actual physical I/O device or which are the devices that correspond to the logical file.
When the number of computer-controlled telephone exchanges, and the services provided by them have increased, demands have arisen for flexible management of data transmission to a centralized operation and maintenance unit i.e an operation and maintenance center, OMC. When the number of exchanges subjected to an operation and maintenance center OMC, no matter whether it is an areal OMC or the master OMC, or the amount of information sent by the exchanges increases, a situation arises in which the capacity of data transmission of the OMC or the capacity of I/O devices is not sufficient.
The prior art knows two ways to solve the problem. Firstly, the capacity may be increased either by increasing the number of data communication units DCU of the OMC. Secondly, it is possible to increase the number of above-mentioned I/O devices, and distribute the load more evenly among them.
The prior art solutions, however, have a few drawbacks. Upon changing the installation of the operation and maintenance center OMC, it is a difficult operation to change the linkages of many of the I/O tasks of the numerous exchanges under the control of the OMC, so that they are correctly connected to different I/O devices of the OMC, the installation of which has been changed. For example, a typical case of expanding the OMC for distributing the calculation load is adding a specific charging storage unit including its hard disk. The charging reports arriving from the exchanges are thus directed to this charging storage unit. An increasing amount of reporting also requires that data communication units be added to the OMC, so that the increased need for data transfer of the operation and maintenance channels can be handled. These changes made in the operation and maintenance center OMC, in turn, result in that the data transfer control functions must be changed in all exchanges to the I/O devices of the OMC, so that they correspond to the new configuration.